---
type: WebApplication
title: "Macro Calculator: Calories, Protein, Carbs, Fat"
description: "Free macro calculator using the Mifflin-St Jeor equation. Enter age, height, weight, training days and goal to get calories, protein, carbs and fat."
resource: https://quietgains.app/tools/macro-calculator
tags: ["macros", "calories", "protein", "mifflin-st-jeor"]
timestamp: 2026-09-22
---

# How many calories, and how much protein?

A macro calculator estimates daily calories from resting energy and activity, then splits them into protein, carbohydrate and fat. Seven inputs in. Calories, protein, carbs and fat out, with every step shown.

## How the answer adds up.

Resting energy by Mifflin-St Jeor, times an activity factor, then the goal applied.

1. Resting energy: 1,780 kcal (10 × 80 kg + 6.25 × 180 cm − 5 × 30 + 5)
2. Your training week: 2,759 kcal (1,780 × 1.55 activity factor)
3. Goal applied: 2,760 kcal a day (2,759 to the nearest 10)

Worked example: a 30-year-old man, 180 cm, 80 kg, training 4 to 5 days a week, maintaining.

| Target | Amount | Working |
| --- | --- | --- |
| Calories | 2,760 kcal | 2,759 to the nearest 10 |
| Protein | 128 g | 1.6 g × 80 kg |
| Fat | 92 g | 30% of 2,760 kcal ÷ 9 |
| Carbs | 355 g | the 1,420 kcal left over ÷ 4 |

## Formula and sources

Resting energy uses the Mifflin-St Jeor equation: for men 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5, for women the same with − 161 in place of + 5 [1, 2].

Maintenance is resting energy times an activity factor: 1.2 for 0 to 1 training days a week, 1.375 for 2 to 3, 1.55 for 4 to 5 and 1.725 for 6 to 7.

A weight goal moves calories by the weekly change × 7,700 kcal ÷ 7 a day, capped at 25% of maintenance below it and 15% above it. Calories round to the nearest 10 and stay between 1,200 and 5,000.

Protein is 2.0 g per kg of bodyweight to lose fat, 1.8 to gain and 1.6 to maintain. The ISSN position stand reports 1.4 to 2.0 g per kg a day for people who exercise [3].

Fat is 30% of calories, inside the 20 to 35% range the Institute of Medicine sets for adults [4]. Carbohydrate takes the calories left over, divided by 4.

These are the starting conventions of the QuietGains app. This page runs the same arithmetic, tested against the app’s own nutrition target vectors.

1. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. "A new predictive equation for resting energy expenditure in healthy individuals." Am J Clin Nutr 1990;51(2):241-247. doi:10.1093/ajcn/51.2.241
2. Frankenfield D, Roth-Yousey L, Compher C. "Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review." J Am Diet Assoc 2005;105(5):775-789. doi:10.1016/j.jada.2005.02.005
3. Jäger R, et al. "International Society of Sports Nutrition Position Stand: protein and exercise." J Int Soc Sports Nutr 2017;14:20. doi:10.1186/s12970-017-0177-8
4. Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: National Academies Press; 2005. doi:10.17226/10490

## Reading the result

### Protein per kilo

As a share of calories, protein moves whenever calories do. Set per kilo of bodyweight, it stays where it is.

### Fat first, then carbs

Fat is 30% of calories. Carbs take whatever is left.

### The same numbers as the app

The QuietGains app works out its starting targets from the same inputs with version 3 of its nutrition engine. This page gives the same answer.

## Related

- [Energy left today](https://quietgains.app/tools/energy-left-calculator)
- [Body composition](https://quietgains.app/tools/ffmi-calculator)
- [Protein per kilo](https://quietgains.app/journal/protein-per-kilo)
- [Every free tool](https://quietgains.app/tools)

The app logs food against these. QuietGains sets the same targets from your profile and counts every meal against them. Arithmetic only. Not medical advice.